M115

When the W115 replaced the fintail in 1968, Daimler-Benz renumbered its petrol engines to run in step with the vehicle series — so the four became the M115, though it was the M121 with very little altered. The counterflow aluminum head, the five-bearing crankshaft in a gray-iron block, the roller-chain-driven overhead camshaft working two valves per cylinder through rocker fingers: all of it carried straight over. Two liters in the 200, 2.2 in the 220, and from 1973 a 2.3 for the 230.4, at which point the old block had nothing left to give.

It followed the range into the W123 in 1976 and was replaced there in 1980 by the crossflow-head M102, which was better on almost every measure. That should have been the end of it. Instead the M115 kept working — in the Düsseldorf T2 vans, in the 208 and 308 of the Bremen T1 range, and above all in the 230 G, where it drove the first-generation W460 G-Wagen from 1979 until 1985, some thirty years after the design had first appeared as the M121.